Why is My AC Unit Not Turning On? | Rinaldi's A/C & Electrical

Why is My AC Unit Not Turning On?

How To Fix Your A/C Unit and Make Your Home Comfortable Again
Read Time: 5 minutes
Nov 7, 2022
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If your AC will not turn on it could be caused by built-up ice, a wiring issue, low refrigerant levels, a dirty air filter and coils, or a faulty thermostat. To figure out the issue, access five spots in your home: the ac switch, filter, thermostat, circuit breakers, and drain pan. If you cannot DIY a solution, call in a professional to repair your unit. Following proper maintenance will help prevent a reoccurring problem.

Common Reasons an AC Won’t Turn On:

For some reason your AC just won’t switch on. Understanding why your AC won’t start makes directing an HVAC specialist to the source of the issue easier, reducing the time it takes to get your AC back up and running.

Built-Up Ice

If you’re experiencing built-up ice on the condenser coils in your AC unit, there is cause for concern even if it is a winter month. AC units will freeze up for a few reasons. The main reasons being a problem with refrigerant levels or limited air flow, both of which can result in permanent damage to your unit if not addressed.

If your refrigerant is low or leaks, the moisture will freeze as the pressure drops and cause ice to build-up. Limited air flow will result in a similar situation.

Woman adjusting thermostat

Faulty Thermostat

The thermostat is the control center for your entire AC system. Without it working properly, your AC will not turn on. This fix could be as simple as replacing the batteries or as complex as handling a faulty capacitor.

Other common complications with your thermostat results from dirt in the thermostat itself. To fix this problem start by turning the thermostat off and removing the cover. You’ll need to clean these four areas with bond paper or a soft cloth:

  • Bimetal plate
  • Top of thermostat body
  • Mounting plate
  • Between contacts

If your AC will not turn on after cleaning then it’s time to call in a professional.


Your AC might not be turning on because of an issue with the wiring itself. If there is a loose wire or messed-up fuse your AC may not run properly. A short in your wiring, caused by too much electricity being pushed through the wire, is another wiring issue that can cause the unit not to turn on.

Playing with electrical malfunctions can be dangerous and is better left to the professionals. Contact your local HVAC technician for assistance if you suspect a wiring problem.

Dirty Filter or Coils

If your air filter has accumulated too much dirt it could impede airflow and lead to frozen coils. A similar situation can arise when condenser coils become dirty. Both situations cause your AC unit to work harder and can result in further damage.

Check These 5 Places When AC Troubleshooting

Before calling your HVAC technician or when they’re in route to your home, check out these areas to see if there is a potentially simple solution:

  1. AC Switch – This is the easiest fix and while it’s unlikely, check your AC switch to ensure it isn’t set to OFF. It could’ve easily been switched off by someone thinking it was a switch to another home appliance.
  2. Air Filter – When was the last time you changed your air filter? If it’s been more than three months since a change, you could be dealing with a clogged air filter. Simply switch it out for a new filter and test out your AC unit.
  3. Thermostat – Check your thermostat to ensure it’s on and set below the current room temperature. Your AC will not turn on if the thermostat is set to the same temperature as the room or a setting warmer than the room.
  4. Circuit Breakers – This requires a trip to your home’s power panel. Flip the AC Unit switch off and back on again. Note: Only switch it once, you don’t want a broken AC unit and an electrical fire.
  5. Drain Pan – If there is a clog in your drain pan it could cause the pan to become full. To prevent flooding, most units have a float switch that will shut the unit down entirely. When the float switch is consistently triggered due to a drain pan, it will appear that the unit it has broken.

Two ac units outside of home

When to Replace versus When to Repair

Old Unit

Your AC unit has a lifespan of 15 to 20 years, depending on the manufacturer and model. Lifespan is also dependent on proper maintenance and size for your home. A unit that is too large for your home may actually breakdown quicker due to constantly switching on and off.

Once your unit is on its fifteenth year it’s time to consider finding a replacement, especially if it’s already started giving you trouble.

High Repair Cost

Certain repairs, such as replacing a compressor or adding refrigerant can cost almost as much as a new unit. This raises the question of how much you are willing to pay to fix a unit. If it makes more sense to buy a new unit for nearly the same cost, it may be a more financially savvy decision.

It’s good to go into a repair with a limit on how much you’re willing to pay to fix the unit and at what point you will pivot to replacing instead.

Consistently Broken

If your unit is constantly breaking for one issue or another, especially if these are major repairs, it could be time to consider replacing your current unit for something new.

Think about all the repairs you’ve recently had to make on your current unit. What is the grand total you’ve put into the unit? Does it make sense to sink more into the unit or to invest in a newer model with fewer problems?

Solutions and Preventative Maintenance for AC Units

Your goal with any repair should be to learn how to prevent future repairs. Most times that an AC unit is broken there is relevant maintenance practices that could have prevented the need for repair to begin with.

Regularly Change and Clean AC Filters

Change your filter for a fresh one every 90 days. If you have a vacation home you can stretch that time frame to every six months. However, if you have pets you should cut the average three months down to monthly changes. Pets can clog an air filter quicker due to loose hair and additional dirt being tracked into the home.

Vacation Homes Every 180 Days
Average House Every 90 Days
Homes with Pets Every 60 Days
Multiple Pets or Allergies Every 45 Days
Full Set ~26 months

Clean Coils and Debris from Unit

Keep your unit running by cleaning the coils on your unit and prevent blockages by clearing away debris. You can clean coils with compressed air, household detergents, or a cleaner made specifically for cleaning AC coils. When using chemicals, ensure that all suds are washed away when you’ve finished cleaning. You don’t want to leave behind any residue.

If you don’t feel comfortable cleaning the coils on your unit, call a professional to complete this task during a maintenance visit. The best time to do this is in the months leading up to summer when your AC usage will increase exponentially.

Straighten Coil Fins

Check that your coil fins aren’t bent when performing cleanings. Bent coil fins can make it more difficult for your unit to run. This can result in a unit that is increasing your electric expenses or simply isn’t working properly.

Use a fin comb to straighten coils. Make sure that the set you have matches the Fins Per Inch (FPI) of your AC unit to prevent damage. If you aren’t sure exactly what size you should get for your unit at the time of order, you can find a comb with interchangeable heads or six heads.

Schedule a Maintenance Visit with a Professional

During preventative maintenance calls, our team will access all parts of your A/C unit, from the evaporator coil to the air filter and thermostat, to keep your unit from generating more money-wasting problems.

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